Power hand tool attachment



y 1, 1956 H. F. BRENHOLTS 2,756,854

POWER HAND TOOL ATTACHMENT Filed March 19, 1954 4 1 3 E i L l Ii" lllllllllflllllllllllllllIlllllllllllllfll! H H l|lIllllllllllllllllllllllllllllllllllllllilllllill v I u llllllllllllllllllillllllllllilllllllllllllllillll 5 IN V EN TOR. HOWARD F. BRENHOLTS.

BY 4 47, M ma W ATTORNEYS.

POWER HAND TOOL ATTACHMENT Howard F. Brenholts, Bethe], Pa., assignor to Drilo Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Application March 19, 1954, Serial No.-417,432

2 Claims. (Cl. 192-34) My invention relates to power-driven hand tools, and consists in an attachment for electric hand drills, .say drills of the pistol grip type, or of the cross-handle type, which are in such wide use at the present time, it being noted that electric hand drills, so-called, are in fact not drills at all, but are electric motor units for driving drill bits.

The object of the invention is to provide an attachment which may be readily engaged to the drive shaft of an electric hand drill, to serve as a variable speed drive for tools other than the drill bits normally operated'by such electric hand drills. By way of example, I mention screw driver bits, socket wrenches, and other rotary tools, as the implements which a conventional electric hand drill may be adapted to drive through the instrumentality of my device. Indeed, where variation in speed and yieldability of the-rotative stress are desired in the driven tool, the device of this invention may be used withdrill bits which otherwise are driven directly by an electric drill'or drive unit.

More particularly, my invention consists in a certain new and useful combination of positive mechanical interlocks and a friction clutch in the mechanical torque train between the rotor of the electric drill and the driven tool.

The assembled drive unit and tool may be securely grasped and guided in the hands of the user, without any danger of the moving parts pinching or otherwise injuring the fingers. Sturdiness in construction, durability and efliciency in service are features to be noted in the design of the invention.

The invention will be understood upon reference to the accompanying drawings, in which:

appear, to receive the conical clutch element 6 of the drive spindle in 'a frictional driving engagement.

At its lower end 9 the driven spindle forms a tool bit carrier, which lower end extends from the housing 5 to permit ready attachment and removal of the various bits which are to be driven. Between the clutch elements 6 and 8 a coil spring 10 is arranged, the clutch elements being socketed as shown in Fig. 2 to receive and stay the ends of the spring. The spring serves normally to hold the clutch elements out of engagement with one another.

The housing 5 is floating or free turning, formed as a two-part block, as shown, to provide a hand-hold for the user of the tool, as well as to provide an all-enclosing housing that is relatively rotatable to both of the clutch elements 6 and 8 of the two spindles which it encloses. In service the upper end 3 of the drive spindle, projecting upward from the hand-hold 5, is engaged in the chuck of a power-driven hand drill, with the ends of the jaws of the chuck bearing against an abutment portion 40 on the shoulder 4 of the spindle, to transmit the manually applied axial thrust, as will presently appear. It will be noted that the body of the hand-hold is formed of two cup-shaped'members 11 and 12, united in a threaded joint 13 and forming an externally smooth and rounded body that may be readily and comfortably held in one hand of the user, while the motor drive unit is grasped in the other hand. The external surface of the hand-hold body 11, 12 may be knurled, as at K, to assure security in the grip of the user.

When the electric hand drill is in operation, the drive spindle 2 is powerfully rotated, say at a speed of from Fig. 1 is a view in side elevation of a drill attachment embodying the invention;

Fig. 2 is a view of the device in vertical section;

Fig. 3 is a view in cross section and to larger scale, showing on the plane IIIIII of Fig. 1 the jaws of the chuck of an electric drill engaged to the driving spindle of the device;

Fig. 4 is a View in side elevation of a tool adapter for use with the device; and

Fig. 5 is a view in side elevation of one of the clutch elements of the device, illustrating a modification.

The attachment or device of the invention includes a driving spindle 2, which is of reduced diameter at its upper end 3 for engagement by the jaws of the conventional chuck of an electric hand drill. It will be perceived that the shoulder 4 between the portions 2 and 3 of the'drive spindle provides an abutment against which the ends of the chuck jaws may bear, and in the assembled structure this shoulder 4 lies substantially flush with the top of a housing 5, later to be described in .detail. At its lower end the driving spindle is provided :with a clutch element, advantageously a conical clutch element 6 of hardened steel. Arranged in axial alignment with the drive spindle 2 is a driven spindle 7, provided at its upper end with clutch element in the form of a socketed member 8 of hardened steel, adapted, as will presently 1700 R. P. M. to 22.00 R. P. M., the normal speed of such a drill, but the hand-hold may be readily held in the hand against rotation. The driven spindle 7 normally remains at rest, since the clutch elements are held out of engagement by the spring 10. It will also be noted that the bodies of the two spindles are rotatably engaged and supported by the housing or hand-hold 5; that is, the body portions of the spindles located immediately adjacent to and outward from the clutch portions 6 and 8, respectively. These body portions of the spindles, which thus constitute journals rotatably borne by the body of the housing 5, are of relatively large diameter. It is to be noted that the edges of the openings in the housing, through which .the said journal portions extend are each located at a substantial interval radially inward from the side surface ,of the housing, whereby the fingers of the hand grasping the housing do not lie close .to the edges of .the joints where there is a relative rotation between the housing and the journal portions extended therethrough. By virtue of these features a sturdy assembly of the spindles. is assured, to withstand wear and endure relatively great stresses. The rotatable engagement of the clutch elements with the housing 5 is limited to annular portions 14 and 15 of relatively small areas, thereby tending to minimize frictional drag between the relatively rotating parts, and to facilitate the use of the housing 5 as a handle or hand-hold, particularly when operating pressure is applied to drive the screw driver bit 16, or other tool.

The tool-securing lower end of the driven spindle is formed with a bore which receives the shaft portion 17 of the screw driver bit 16, shown in Fig. 2, and in such bore is provided a rigid cross-pin '19, upon which the notch 18 in the upper end of the tool shaft is positioned, thus providing a detent which insures that the tool bit cannot rotate or slip relative to the driven spindle 7. The tool bit is provided with an external collar or shoulder 21, and a tubular keeper 22 is internally threaded, as at 20, for engagement upon the externally threaded end 9 of :the'driven spindle, such tubular keeper having an inter-nalcollar or. shoulder that engages the .tool shoulder 21 and clamps it against the end of the driven spindle. thus affording perfect attachment of the tool bit to the spindle, and yet providing for ready removal and interchange of tool bits.

In order to drive a screw, the upper end 3 of the driving spindle is chucked in the electric drill, and the head of the screw is engaged by the screw driver bit; next the user bears downward upon the electric drill held in the right hand, say, while steadying the driving device by holding the housing 5 in the left hand. The thrust thus created is transmitted by the chuck jaws of the drill against the rounded abutment portion 40 on the shoulder 4- of the rotating driving spindle 2, and under the effect of the thrust imparted to the rotating spindle 2 the spring is compressed, and the clutch members 6 and 8 are closed in frictional engagement, thereby positively rotating the spindle 7 and the screw driver bit carried thereby. The screw is driven home, as will be manifest.

It will be understood that the rotative speed of the usual electric hand drill is normally too great for driving the screw driver bit, and it is to be noted that the required reduction in speed is obtained by slipping the clutch. That is to say, the pressure or thrust applied to the spindle 2 is such that the conical clutch element 6 slips within the socket element 3, and thereby causes the screwdriving bit to rotate at much lower speed than the motor of the electric hand drill, while providing mechanical advantage in the torque transmitted. By varying the thrust applied to the spindle 2 the speed of rotation and the torque developed may be regulated to suit the particular job to be done. Furthermore, when the screw reaches fully driven position the clutch will slip and will thus prevent the head of the screw from being twisted off, as might be the case if an unyielding drive were provided for the screw driver bit. Furthermore, the friction clutch may slip and permit the bit to be freed from the kerf in the head of the screw, without damage to the surrounding surface of the work.

Fig. 4 illustrates an adapter bit 31 that may be secured in the device in place of the screw driver bit 16. The lower or outer end of the adapter bit is provided with a square tip 32, from one side of which a spring-backed ball 33 extends, whereby various bits, socket wrenches and other tools, provided with a snap-on socket, may be readily secured upon the tip 32.

The chuck of the electric drill engaged to the driving spindle 2, 3, together with the clutch elements 6 and 8, and the driven spindle 7, form a mechanical train, through which the torque developed by the rotor of an electricdrill is transmitted with selected speed reduction and force to the driven tool or hit. As already mentioned, the selected speed and transmitted torque may be determined by the degree of the manual pressure applied to the electric drill to engage the clutch elements 6 and 8. With this in mind, it is important to note that the mechanical torque train of the device of my invention includes two positive mechanical interlocks between the driving rotor of the electric drill and the driven tool bit, and between the two positive mechanical interlocks a frictional clutch is provided.

More specifically, the stem or spindle portion 3 is formed with three grooves 34- that extend longitudinally of such portion, and each groove is in cross section rounded to receive in snug engagement the clamping edge of one of the three jaws 35 of the chuck of the electric drill that drives the device, as may be understood upon considering the cross-sectional view of Fig. 3. This engagement of the driving chuck jaws with the spindle portion 3 provides the first mechanical interlock in the torque train mentioned.

The second mechanical interlock is provided by the engagement 18, 19 of the bit to the driven spindle 7 of the device, while the elements 6, 8 provide the frictional clutch between the said positive mechanical interlocks of the train. This specific combination of interlockingand frictional units is very efiective, and forms the cardinal feature of the device of my invention. Advantageously the grooves are formed in the spindle portion 3 in a coining operation.

A subsidiary, yet important, feature of my device is found in the abutment portion 40, which portion is engaged by the outer tips or ends of the chuck jaws that clamp the electric drill to the spindle portion 3. The axial thrust which the user manually applies, by exerting thrust or pressure upon the electric drill, is transmitted by the ends of the chuck jaws bearing against portion 40. The portion 40 provides mechanical reinforcement in the region where the spindle portion 3 of reduced diameter is integrated with the driving spindle portion 2 of larger diameter, thus forming a wear-resisting element between the chuck jaws and the engaged driving spindle in the region where fracture or mechanical failure has hitherto occurred in service.

Fig. 5 illustrates that the male member 6 of the clutch may be provided with one or more radial or longitudinal grooves 60, say from .020" to .100" in depth and from .125" to .250" in breadth. The groove or grooves enhance the frictional engagement of the two clutch members 6 and 8. Each groove acts as a cleaning slot that picks up any particles of metal, dust, or other foreign matter that enters between the conical surfaces of the two clutch members 6 and 8, and that may tend to reduce the frictional efiiciency of the clutch. The material accumulating in the groove works its way upwardly to the top of the male clutch member, whence it may be removed at will. The radial groove or grooves are largely responsible for the successful application of the metal-to-metal type of clutch engagement.

In modification, the radial groove or grooves may be provided in the female clutch member 8. The groove or grooves not only provide the advantages indicated, but they also serve to augment the dissipation of heat from the clutch.

The usual electric hand drills of today are driven by reversible electric motors, wherefore it will be understood that the bits described may be driven to remove, as well as to install screws, nuts and the like.

The device of my invention has widened the utility of electric hand drills to a great variety of uses not heretofore available to the public. A single electric hand drill becomes in efiect a great number of power tools. Many modifications of the structure described will be understood to be within the spirit of the invention defined in the appended claims.

I claim:

1. In a driving device for an electric drill having a rotor equipped with a chuck, said device comprising a driving spindle having a portion at its upper end for engagement by jaws of said chuck and a frictional clutch element at its lower end, a driven spindle having a frictional clutch element at its upper end to receive said clutch element of the driving spindle, means for securing a tool to the lower end of the driven spindle, and a floating housing enclosing said clutch elements and providing hearing for said spindles and also providing a hand-hold for said device, with both the chuck-receiving and tool-securing ends of said spindles severally accessible at the opposite ends of said hand-hold without danger to the fingers of the user during relative rotation between the hand-held and the spindles; the invention herein described wherein a torque train is provided between said rotor and said tool comprising two mechanical interlocks between which said frictional clutch elements are operable, said upper portion of the driving spindle being of reduced diameter and projecting from said housing and including a plurality of longitudinally extending grooves for engagementseverally by said chuck jaws to provide one of said mechanical interlocks between said rotor and tool, and said means for securing the tool in the driven spindle including a detent carried by the driven spindle and comprising the second of said mechanical interlocks between which said frictional clutch elements operate in said torque train.

2. In a driving device for an electric drill having a rotor equipped with a chuck, said device comprising a driving spindle having a portion at its upper end for engagement by jaws of said chuck and a frictional clutch element at its lower end, a driven spindle having a frictional clutch element at its upper end to receive said clutch element of the driving spindle, means for securing a tool to the lower end of the driven spindle, and a floating housing enclosing said clutch elements and providing bearing for journal portions on said spindles and also providing a hand-held for said device, with both the chuckreceiving and tool-securing ends of said spindles severally accessible at the opposite ends of said hand-hold without danger to the fingers of the user during relative rotation between the hand-hold and the spindles; the invention herein described wherein a torque train is provided be tween said rotor and said tool comprising two mechanical interlocks between which said frictional clutch elements are operable, said upper portion of the driving spindle being of reduced diameter and projecting from said housing and including a plurality of longitudinally extending grooves for engagement severally by said chuck jaws to provide one of said mechanical interlocks between said rotor and tool, a spindle-reinforcing portion integrally formed in the body of said driving spindle where the grooved projecting spindle portion of reduced diameter merges with the journal spindle portion of larger diameter, said spindle-reinforcing portion comprising an annular shoulder accessible externally of said housing to the ends of the chuck jaws engaged to the grooved spindle portion for transmitting thrust applied through the chuck jaws to said driving spindle, and said means for securing the tool in the driven spindle including a detent carried by the driven spindle and comprising the second of said mechanical interlocks between which said frictional clutch elements operate in said torque train.

References Cited in the file of this patent UNITED STATES PATENTS 852,320 Dicks Apr. 30, 1907 1,447,626 Partlow Mar. 6, 1923 2,045,452 Emrick June 23, 1936 2,354,526 Lapsley et a1. July 25, 1944 2,501,386 Gibbs Mar. 21, 1950 

